Browsing by Issue Date, starting with "2023-09-28"
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- Biofilm Formation by ST17 and ST19 Strains of Streptococcus agalactiaePublication . Silvestre, Inês; Borrego, Maria José; Jordão, LuísaBacterial biofilms are an important virulence factor with a vital role in evasion from the host immune system, colonization and infection. The aim of the present study was to evaluate in vitro the effects of three environmental factors (H+ , glucose and human plasma) in biofilm formation, by carrier and invasive S. agalactiae strains of ST17 and ST19 sequence types, including DNase producers and nonproducers. Bacteria ability to assemble biofilms was classified based on crystal violet assay. Biofilm formation was also monitored by scanning electron microscopy. Depending on the growth medium used, each bacterial isolate could fit in different biofilm production categories. Our data showed that optimal conditions for S. agalactiae biofilm assembly were reached after 48 h incubation at pH 7.6 in the presence of glucose and inactivated human plasma. In the presence of inactivated human plasma, the biofilm biomass of ST19 strains experienced a higher increase than ST17 strains. The composition of the extracellular polymeric matrix of the three strongest biofilm producers (all from ST17) was accessed by enzymatic digestion of mature biofilms and proteins were shown to be the predominant component. The detailed identification of the extracellular protein components should contribute to the development of new therapeutic strategies to fight S. agalactiae infections.
- Deciphering a potential toxic synergy between persistent organic pollutantsPublication . Puskar, Ljiljana; Jordão, LuísaPlastic, massively used in everyday life, inevitably accumulates in the environment, becoming a persistent pollutant due to its reduced and/ or extremely slow recyclability1. Plastic particles in the micro and nano range, known as micro (MP) and nanoplastics (NP), respectively represent a huge ecotoxicological challenge. Due to their high surface areas, they might ad/absorb other persistent pollutants with similar chemical properties, such as polycyclic aromatic hydrocarbons (PAHs), with unpredictable effects on persistence and distribution in the environment2. MPs/NPs, with or without pollutants ad/absorbed, could enter the trophic chain at the level of invertebrates, inflicting toxicological effects through all levels of the ecosystem3. Polystyrene MPs and PAHs previously found in water samples (e.g. fluoranthene, phenanthrene)4 and known to be adsorbed by MPs (Pyrene, benzo(a) pyrene)5 will be used in the study. PAH’s mixtures will be used to mimic environmental samples and single compounds will be used in order to understand the individual contribution of each compound for the observed toxic effect. This experimental approach will also allow to evaluate a potential synergy between compounds with effect on toxicity. Since PAHs and MPs have similar chemical properties, they are known to adsorb to each other. We will use PAHs adsorbed to MPs to test higher concentrations of PAHs (not soluble in aqueous solutions such as cell culture medium) and to document the intracellular distribution of adsorbed versus free PAHs. Concerning MPs only one material will be used at this stage. Polystyrene was selected because it is commercially available in spheres suitable for internalization by HepG2 cells and was previously isolated from environmental samples 4. This study could contribute to identify differences in toxicity and contribute to the elucidation of the underlying toxicity mechanisms using molecular biology protocols, light/electron microscopy and FTIR micro/spectrometry.
- Aplicação de biomarcadores de efeito na biomonitorização humana: teste do cometa e teste do micronúcleoPublication . Louro, HenriquetaSobre a utilização de biomarcadores de efeito em estudos de biomonitorização humana.